This invention relates to the dispensing of expanded foams and, more particularly, to an improved foam dispensing gun.
Various foam dispensing guns have been proposed and used for mixing and expanding isocyanate, polyol and other foam components into polyurethane foam. When these components are mixed in proper proportions, as is well known, they react quickly to form an expanded foam and begin to solidify. Additionally, the component parts of the foam can begin to solidify by reacting with moisture available in the air. Thus, provision must be made for keeping the foam dispensing apparatus free from buildup of the component parts and the resulting expanded foam so that its control valves and passageways do not become clogged, rendering the apparatus inoperable.
Some prior foam dispensing apparatus required dismantling after each application in order that the dispenser be cleaned. Most foam dispensers of recent design have utilized integral means for cleaning the gun, with a solvent being introduced to the dispenser after its use to flush the expanded foam and unreacted components therefrom. However, experience with apparatus of this general nature has shown that, while an improvement over the dispensers which had to be disassembled for cleaning, adequate cleaning of the dispenser is not always provided.
The expanded foams generated by these apparatus are commonly used for insulation in, for example, refrigerator shells. Such shells require a fixed volume of foam--too much foam will split the shell, too little and the shell will not be adequately insulated. However, the foam dispensing guns of the prior art are not provided with means that enable the user to consistently dispense the identical volume of foam with each use of the dispenser.
It is, therefore, an object of the present invention to provide a foam dispensing apparatus of relatively simple construction, yet which may be readily cleaned after use. A related and more specific object provides a foam dispensing apparatus having an improved valve arrangement for controlling the flow of the foam components through the dispenser so that the valves, the passageways and the mixing chamber may be readily cleaned without disassembly, thus permitting the apparatus to be kept in operative condition at all times.
A further object lies in the provision of a foam dispensing apparatus having a configuration which promotes uniform mixing of the foam components.
Yet another object is to provide a dispensing apparatus valve system which is capable of timed actuation so that only a predetermined amount of expanded foam will be produced.